[Multilingualism and Dementia: From the Studies in Brazil and Taiwan]

Our studies in Brazil and Taiwan revealed that the prevalence of dementia was independent of environment, culture, and use of multilingualism. However, language deterioration in dementia was found to be related to its frequency of use and the environment, and both language, and deterioration were asymmetric. Although the cognitive reserve and protective effect of multilingualism on dementia were shown, the decline in language function was found to be related to psychiatric symptoms of dementia, delusions, and depression which were relieved by providing a reliable language environment. It was suggested that language function evaluation should be considered for dementia care.